For at least a century, there have been various approaches to the problems of (1) absorbing or dampening the shocks, jerks or surges that are generated in lines or ropes under certain conditions, and (2) introducing resilient forces into a line when it is tensioned. One such problem is present where a boat is moored to a dock or pier, and waves repeatedly jerk the line as soon as it becomes taut. It is also present when a boat is being stopped upon coming into a dock. Such jerking can generate large forces that strain the line (and the elements to which it is connected) to a high degree, can damage the boat, and can cause occupants of the boat to fall.
Prior-art approaches toward solution of the problem have been deficient in one or more of the following (and other) ways: relatively high cost; inability to dampen sufficiently large forces; inability to keep the boat moored even if the shock absorber breaks; inability to use helical compression spring means; absence of a casing that fully encloses the mechanism; and inability to permit a lengthening of the line that is much larger than the shortening of compression spring means incorporated in the shock absorber.